This invention relates to an apparatus for raising and lowering a low-boy trailer between its driving and loading positions, and in particular to such an apparatus which is completely self-contained.
A low-boy trailer is arranged so that its front end can be lowered to the ground and disconnected from the towing vehicle in order to facilitate loading. This is accomplished by using a gooseneck to interconnect the trailer to the tractor, with the front end of the gooseneck being attached to the tractor by means of a fifth wheel and its rear end being attached to the trailer by means of a pin coupling. Accordingly, when the rear end of the gooseneck is raised or lowered it also moves the front end of the trailer to a raised or lowered position.
Heretofore the gooseneck has been raised and lowered by means of hydraulic jacks which are attached to the sides of the gooseneck and, in certain circumstances, this arrangement has not been effective, at least in raising the trailer. This is due to the fact that the jacks raise the gooseneck by having their rams extended while in contact with the ground on which the trailer rests. However, since trailers of this type generally are used for transporting construction equipment, they are often used on terrain which is muddy or otherwise will not support the weight of the trailer on the limited area of the rams, rams, even when they include positioning pads. In this event the rams tend to sink into the ground rather than lifting the trailer.
The present invention overcomes the shortcomings and limitations of the prior art lifting apparatus for low-boy trailers by providing a lifting system which is self-contained on the gooseneck and the trailer and is not required to interact with the surrounding terrain. The lifting apparatus comprises extensible piston cylinders which are attached pivotably at their cylinder ends to the gooseneck. The rams of the piston cylinders slidably contact ramps on the trailer at points defined by fore and aft stops. Thus when the rams of the piston cylinders are extended, the points at which they are connected to the gooseneck are moved away from the points at which they contact the trailer, causing the trailer and gooseneck to rotate in opposite directions about their common pivot point at the pin coupling. The end points of the piston cylinders and the pivot point are arranged relative to one another so that as this occurs the rear end of the gooseneck and the front end of the trailer are raised. Conversely, as the piston cylinder rams are retracted the gooseneck and trailer rotate in opposite directions about the pivot point and the front end of the trailer is lowered.
In order to provide lateral stability the rear portion of the gooseneck is bifurcated into a pair of side-by-side arms and one piston cylinder is provided for each of these arms. In addition, the rear portions of the arms are made hollow and extend rearwardly a sufficient distance so that the piston cylinders remain enclosed within the gooseneck throughout their complete range of extension.
Locking means are provided to couple the rams pivotally to the trailer thereby locking the gooseneck irrotatably to the trailer and permitting them to be removed from the tractor as a unit. Thus the gooseneck and trailer assembly can be removed and replaced without the necessity of a separate lifting apparatus.
Accordingly it is a principal object of the present invention to provide a lifting apparatus for low-boy trailers which is entirely self-contained and which does not require interaction with the ground on which the trailer is supported.
It is the further object of the present invention to provide such a device which will raise the trailer higher than its normal driving position to provide temporary increased ground clearance for the trailer.
It is a still further object of the present invention to provide such a device where the piston cylinders which provide the lifting are entirely enclosed within the structure of the device.
It is a still further object of the present invention to provide such a device which allows locking the gooseneck irrotatably to the trailer for removal as a single unit.
The foregoing objectives, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.